Question

if N ball hits elasticity and normally on the surface per unit time and all the balls of mass M are moving with same velocity u then the force on the surface is

Answer 1

When a ball hits normally on surface elastically then it rebounds with same velocity.

F = m * dv/dt
F = nM * (u - (-u)) / t
F = 2nM / t
Given that n/t = N
∴ F = 2NMu

Force on the surface is 2NMu

Answer 2

F=nma

F=m(v-u)/t

here u=u and v=-u

thus force per unit time is

F=nm(u-(-u))

F=2mun

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